The present disclosure is generally directed to a method of detecting analytes in a microfluidic sample, and a system for performing the same.
Assays are often used in the biochemical, medical and environmental fields to detect the presence and/or concentration of one or more analytes. Numerous assays (including immunoassays) are known where the analyte is either an antigen or an antibody. Enzyme-linked immunosorbent assays (also known as ELISAs) have recently become popular, especially in the medical field. This may be due, at least in part, to the fact that an ELISA is capable of quantitatively determining the concentration of, for example, drug(s) in a urine sample, or detecting the presence of, for example, HIV in a blood sample. Particle-based ELISAs have recently been developed, in which antibodies are directly bound to particle surfaces. Such assays generally include the following advantages: 1) an increased surface area relative to binding antibodies to a wellplate surface, and 2) the ability to separate the particles from a liquid phase after reaction using, for example, magnetism or density difference.
Particle-based ELISAs are typically performed by first manually pipetting and mixing the various reagents, including antibodies, antigens, enzymes, other chemicals, and/or carrier particles. Particles are subsequently separated from fluids via the application of some force, for example, magnetism in conjunction with ferrous oxide particles, followed by washing. Spectrophotometric detection is typically performed by transferring (e.g., via a pipette) an aliquot of the particles to a wellplate, and then measuring the wellplate with a bench-scale optical reader. Tests are run independently, or using a simultaneous series, and the results are generally processed manually. Automated ELISA systems have recently been implemented as benchtop models to reduce time and labor costs often associated with manual ELISA systems. These automated systems may, however, require additional bulky and relatively heavy equipment, and/or typically utilize conventional wellplate approaches. Portable, automated systems using smaller, disposable coupons may be a desirable alternative to the benchtop models, however, such systems may be limited in the type of force used for particle separation.